In many situations it is desirable to generate a sound field that includes information relating to the location of signal sources (which may be virtual sources) within the sound field. Such information results in a listener perceiving a signal to originate from the location of the virtual source, that is, the signal is perceived to originate from a position in 3-dimensional space relative to the position of the listener. For example, the audio accompanying a film may be output in surround sound in order to provide a more immersive, realistic experience for the viewer. A further example occurs in the context of computer games, where audio signals output to the user include spatial information so that the user perceives the audio to come, not from a speaker, but from a (virtual) location in 3-dimensional space.
The sound field containing spatial information may be delivered to a user, for example, using headphone speakers through which binaural signals are received. The binaural signals include sufficient information to recreate a virtual sound field encompassing one or more virtual signal sources. In such a situation, head movements of the user need to be accounted for in order to maintain a stable sound field in order to, for example, preserve a relationship (e.g., synchronization, coincidence, etc.) of audio and video. Failure to maintain a stable sound or audio field might, for example, result in the user perceiving a virtual source, such as a car, to fly into the air in response to the user ducking his or her head. Though more commonly, failure to account for head movements of a user causes the source location to be internalized within the user's head.